MODAL COMPENSATION AND THE ATMOSPHERIC-TURBULENCE OUTER SCALE - COMPUTER-SIMULATIONS

The influence of the turbulence outer scale on the Strehl ratio obtain ed with low-order adaptive optics systems is examined by numerical sim ulation. The Karhunen-Loeve approach is used to generate wave-front sa mples. A method that allows construction of the outer-scale-dependent Karhunen-Loeve functions is described. It is shown that the Strehl rat io produced by a second-order adaptive optics correction (tip-tilt, de focus, and astigmatism) is affected quite strongly by the finite outer scale. For the higher-order correction, the effect under study is wea k and appears only when the outer-scale magnitude becomes less than th e aperture diameter. It is also shown that the finite outer scale has a positive effect on the Strehl ratio of the uncorrected long-exposure image. (C) 1998 Optical Society of America.